1. Field of the Invention
The present invention relates to a protective device for preventing an accidental breakdown in an electric distribution system and a damaging of motor devices connected to the system.
2. Description of the Background Art
In an electric distribution system, a circuit breaker and a protective device are provided at each branch point of the system such that in case trouble occurs in the system, the trouble can be detected by the protective device and a disabled part can be disconnected selectively by the circuit breaker activated by the protective device, while still connecting as many of the other normally functioning parts of the system as possible. In order to be able to selectively disconnect the disabled part at the minimum interval, it is necessary to set the operation characteristics of the protective device appropriately.
Usually, this setting of the operation characteristics of the protective device is manually carried out by using a combination of ON/OFF switches, so that the errors may very well be occurring in the setting. For this reason, the inspection and confirmation of the correct setting is indispensable for the protective device.
In inspecting the setting in a conventional protective device, either the switches are inspected by human eyes, or the test of the overloading characteristic of the protective device is carried out.
In such a conventional protective device, when the human eye inspection is adopted the confirmation in a form of the overloading characteristic test cannot be obtained, while when the overloading characteristic test is adopted a large amount of current is necessary and a configuration inevitably becomes more complicated, both of which contributes to a higher cost for the operation.